Electrical connector elements are used in a very wide range of embodiments to connect a generally cable-type conductor to a printed circuit board PCB or to conductor tracks disposed thereon.
Such electrical connector elements are secured to the printed circuit board by means of projecting contact elements, referred to hereafter as connector pins, which in the assembled position are connected in an electrically conducting manner to assigned conductor tracks provided on the printed circuit board. The connector pins are also referred to as solder pins, because they generally engage in openings or holes already present in the printed circuit board and are then soldered to the printed circuit board.
There are numerous variants of connector pins, generally with a round or rectangular cross-section.
The high density of the arrangement of components provided on the printed circuit board means that the smallest possible dimensioning of the electrical connector elements is also desirable.
However the reduction in the size of electrical connector elements reaches a limit due to the safe distance required between the individual connector pins.
Such safe distances are generally required by standard for the reliable prevention of flashover and therefore a short circuit between adjacent connector pins and vary depending on the size of the voltage present at the electrical connector element or at the connector pins.
The specific voltage required to allow current to flow through an insulator, in the case of generic printed circuit board arrangements in particular the air between the adjacent connector pins, is essentially proportional to the length of the path hereafter referred to as the “voltage path”, which the electrons have to cover through the insulator or air to travel from one connector pin to the next connector pin and cause a short circuit. A material-specific electric strength is therefore also specified in the unit [V/mm]. Plastic here has a roughly ten to forty times higher electric strength than the medium air.
The safe distance mentioned above corresponds in conventional electrical connector elements to the voltage path, which is essentially the same as the gap between two connector pins. More precisely the safe distance or voltage path is generally measured as the direct distance between the outer sleeves of two connector pins on a putative connecting line in a normal direction to the axes of the connector pins which generally run in the insertion direction of the electrical connector element, with a safe distance thus measured also being referred to as an “air path”.
Parallel to this a further safe distance is also defined in respect of a “creepage path” the current has to cover along the surface of the printed circuit board to travel from one connector pin to the next. The prescribed “creepage path” safe distance is generally considerably greater than the “air path” safe distance, as the surface of the printed circuit board can become dirty during operation and the dirt adhering to the surface of the printed circuit board, in some instances combined with the presence of a high level of air humidity and condensation of moisture from the air on the printed circuit board, facilitates a short circuit between two connector pins.
The safe distances required by standard are subject not only to the performance category of the electrical connector elements but also to further factors, such as the area of operation of the electrical connector elements, for example whether they are deployed in industrial or domestic networks.
If the printed circuit board also has metal edgings in the region of the openings provided to hold the connector pins, the effective voltage path or “creepage path” the current has to cover between two connector pins can be further reduced. The layer thickness of the solder material used to solder the connector pins to the printed circuit board should also be taken into account here.